Type-B Monoamine Oxidase

By Joseph Knoll

Type-B monoamine oxidase (MAO-B) is the form of monoamine oxidase (MAO) that is insensitive to clorgyline. Clorgyline, 3-(2, 4-dichlorophenoxy)-N-methyl-N-2-ynylpropan-1-amine, is an irreversible MAO-inhibitor substance, structurally related to pargyline. The term was coined and introduced, in 1968, by Johnston, to distinguish between clorgyline-sensitive and insensitive forms of monoamine oxidase (MAO) enzymes, referred to as Type-A monoamine oxidase and Type-B monoamine oxidase, respectively. MAO-B was found to be present in the neurons, astroglia and platelets (Neff and Gorodis 1972) and was primarily responsible for the oxidative deamination of beta-phenylethylamine and benzylamine (Costa and Sandler 1972). In 1971, it was shown that MAO activity progressively increased in the aging brain (Robinson et al. 1971) and, by 1980, it was also recognized that this was due entirely to the increase in MAO-B concentrations in brain tissue (Fowler et al. 1980). The first selective MAO-B inhibitor, (-)-deprenyl/selegiline, an (R) –N- methyl-N-(1-phenylpropan-2-yl) prop-2-yn-1-amine, was identified, in1972, by Knoll and Magyar.